Re: [PATCH v2 4/4] dma-buf: heaps: add chunk heap to dmabuf heaps

[Minchan Kim]

On Tue, Dec 01, 2020 at 04:33:14PM -0800, John Stultz wrote:
> On Tue, Dec 1, 2020 at 4:13 PM Minchan Kim <minchan@xxxxxxxxxx> wrote:
> >
> > On Tue, Dec 01, 2020 at 03:38:14PM -0800, John Stultz wrote:
> > > On Tue, Dec 1, 2020 at 2:55 PM Minchan Kim <minchan@xxxxxxxxxx> wrote:
> > > > On Tue, Dec 01, 2020 at 11:48:15AM -0800, John Stultz wrote:
> > > > > On Tue, Dec 1, 2020 at 9:51 AM Minchan Kim <minchan@xxxxxxxxxx> wrote:
> > > > >
> > > > > Thanks for reworking and resending this!
> > > > >
> > > > > ...
> > > > > > +static int __init chunk_heap_init(void)
> > > > > > +{
> > > > > > +       struct cma *default_cma = dev_get_cma_area(NULL);
> > > > > > +       struct dma_heap_export_info exp_info;
> > > > > > +       struct chunk_heap *chunk_heap;
> > > > > > +
> > > > > > +       if (!default_cma)
> > > > > > +               return 0;
> > > > > > +
> > > > > > +       chunk_heap = kzalloc(sizeof(*chunk_heap), GFP_KERNEL);
> > > > > > +       if (!chunk_heap)
> > > > > > +               return -ENOMEM;
> > > > > > +
> > > > > > +       chunk_heap->order = CHUNK_HEAP_ORDER;
> > > > > > +       chunk_heap->cma = default_cma;
> > > > > > +
> > > > > > +       exp_info.name = cma_get_name(default_cma);
> > > > >
> > > > > So, this would create a chunk heap name with the default CMA name,
> > > > > which would be indistinguishable from the heap name used for the plain
> > > > > CMA heap.
> > > > >
> > > > > Probably a good idea to prefix it with "chunk-" so the heap device
> > > > > names are unique?
> > > >
> > > > That will give an impression to user that they are using different CMA
> > > > area but that's not true. IMHO, let's be honest at this moment.
> > >
> > > I disagree.  The dmabuf heaps provide an abstraction for allocating a
> > > type of memory, and while your heap is pulling from CMA, you aren't
> > > "just" allocating CMA as the existing CMA heap would suffice for that.
> > >
> > > Since you need a slightly different method to allocate high order
> > > pages in bulk, we really should have a unique way to name the
> > > allocator interface. That's why I'd suggest the "chunk-" prefix to the
> > > heap name.
> >
> > Got it. How about this?
> >
> > diff --git a/drivers/dma-buf/heaps/chunk_heap.c b/drivers/dma-buf/heaps/chunk_heap.c
> > index 0277707a93a9..36e189d0b73d 100644
> > --- a/drivers/dma-buf/heaps/chunk_heap.c
> > +++ b/drivers/dma-buf/heaps/chunk_heap.c
> > @@ -410,7 +410,7 @@ static int __init chunk_heap_init(void)
> >         chunk_heap->order = CHUNK_HEAP_ORDER;
> >         chunk_heap->cma = default_cma;
> >
> > -       exp_info.name = cma_get_name(default_cma);
> > +       exp_info.name = "cma-chunk-heap";
> 
> That's still a bit general for the default cma (which can be named
> differently). I think including cma name is important, just adding the
> chunk prefix might be best.
> 
> So something like
>   sprintf(buf, "chunk-%s", cma_get_name(default_cma));
>   exp_info.name = buf;

No problem. Will do that in respoin.
Other than that, can you give any Acked-by or Reviewed-by to save
iteration?